Diaphanous 1 and 2 Regulate Smooth Muscle Cell Differentiation by Activating the Myocardin-Related Transcription Factors

Abstract

Objective-We have previously shown that smooth muscle cell (SMC) differentiation marker gene expression is regulated by the small GTPase, RhoA. The objective of the present study was to determine the contributions of the RhoA effectors, diaphanous 1 and 2 (mDia1 and mDia2), to this regulatory mechanism. Methods and Results-mDia1 and mDia2 are expressed highly in aortic SMCs and in a number of SMC-containing organs including bladder, lung, and esophagus. Activation of mDia1/2 signaling by RhoA strongly stimulated SMC-specific promoter activity in multiple cell-types including primary aortic SMCs, and stimulated endogenous SM ␣-actin expression in 10T1/2 cells. Expression of a dominant negative Dia1 variant that inhibits both mDia1 and mDia2 significantly decreased SMC-specific transcription in SMCs. The effects of mDia1 and mDia2 required the presence of SRF and the activity of the myocardin transcription factors and were dependent on changes in actin polymerization. Importantly, stimulation of mDia1/2 signaling synergistically enhanced the activities of the myocardin-related transcription factors, MRTF-A and MRTF-B, and this effect was attributable to increased nuclear localization of these factors. Conclusions-These

Blood pressure–associated polymorphism controls ARHGAP42 expression via serum response factor DNA binding

“…ARHGAP42 expression is upregulated by RhoA signaling. We and others have shown that RhoA signaling enhances SMC-specific gene expression by promoting the nuclear localization of the myocardin-related transcription factors (MRTFs) (26)(27)(28). In support of this mechanism, Arhgap42 expression in primary rat aortic SMCs was upregulated by sphingosine 1-phosphate, a strong activator of RhoA signaling in many cell types, including SMCs (29), and this effect was abolished by pretreatment with the ROCK inhibitor Y-27632 ( Figure 5A).…”

Functional interactions between phosphatase POPX2 and mDia modulate RhoA pathways

“…The exact mechanism of MAL translocation is not known. It has been reported recently that the activities of MAL can be enhanced by the activation of mDia1/mDia2 signalling (Staus et al, 2007). MAL is highly phosphorylated upon serum stimulation (Miralles et al, 2003).…”

The Histone Demethylase, Jmjd1a, Interacts With the Myocardin Factors to Regulate SMC Differentiation Marker Gene Expression

“…36 Cell Culture, Transient Transfections, and Reporter Assays Multipotential 10T1/2 cells and SMCs from rat thoracic aorta were cultured as described previously. 19,37 For transfection of promoterluciferase and expression constructs, cells were maintained in 10% serum media and transfected 24 hours after plating at 70% to 80% confluence using LT-1 transfection reagent (Mirus) per protocol. Luciferase activity was measured 24 hours posttransfection and is expressed relative to plus empty expression vector.…”